Lamps having a glass press stem usually were used without a separate base by extending lead pins through the glass stem and utilizing the pins directly for engagement with a holding socket, or so formed that a box-like base was fitted to the glass press stem, the base being connected by a cement with the glass press stem, or by a clamp connection.
The multiplicity of bases which were used are undesirable in lamps since ease of interchange is impeded. Halogen cycle incandescent lamps which, usually, have a glass press stem, are used more widely in many applications, and it is desirable to be able to substitute halogen cycle incandescent lamps in places where previously filamentary incandescent lamps without halogen addition were used, the filamentary lamps being connected by bayonet or screw-type bases to standard matching sockets. Halogen cycle incandescent lamps as currently available therefore can be introduced into circuits with bayonet or screw-in sockets only if an adapter is interposed. Adapters are expensive and a large number of different types have to be stocked by supply houses to be able to match the available halogen lamps to the different sockets which are on the market in which the lamps should be introducible.